Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Magnus Danielson]

Hi Jim,

On 08/02/2017 03:04 PM, jimlux wrote:

On 8/2/17 5:16 AM, Magnus Danielson wrote:






BTW, I saw that the JPL receiver at ISS got upgraded to support Galileo.
Cool stuff.


well, not exactly upgraded - the hardware didn't change - being bolted
to the exterior of ISS inside a box inside a box - it was a software
change - which is what Software Defined Radios are all about.


Yeah, I know, it got a software upgrade. :)

Recall when I handed you some clues on how to measure the noise of the 
input of that receiver. Some time-nuttery truely goes to space. :)


Cheers,
Magnus
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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[jimlux]

On 8/2/17 5:16 AM, Magnus Danielson wrote:






BTW, I saw that the JPL receiver at ISS got upgraded to support Galileo.
Cool stuff.

well, not exactly upgraded - the hardware didn't change - being bolted 
to the exterior of ISS inside a box inside a box - it was a software 
change - which is what Software Defined Radios are all about.


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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Magnus Danielson]

On 08/02/2017 01:20 AM, jimlux wrote:

On 8/1/17 12:11 PM, Graham / KE9H wrote:

Dider:

This is a CDMA signal. (With a 'chip' rate that far exceeds the
information
rate.)

If you put a different correlator on every multipath signal, which are
each
differently delayed in time, then they can be independently demodulated.
(Or time shifted and added back together with some quality indicator for
weighting.)
So, in CDMA, multipath is used as a form of (time) diversity reception
and
will improve the signal to noise of the combined signal.

By definition, the signal with the least time delay either is, or is
closest to, the most direct path.

You don't have to necessarily fully demodulate this early signal by
itself,
just know what its timing is. (And remember where it was, if fading in
and
out.)

Since multi-path is a destructive mechanism in most narrow band radio
systems, the above may not be intuitive to people not familiar with CDMA
and "rake receiver" based systems.

Multipath helps, not hurts, these systems, as long as the multipath
delays
are most of one chip apart, or more.



For GPS raw (off the air), when they post process at JPL, they use a
fairly sophisticated correlation process, incorporating an estimator of
the underlying time delay trajectory: you can use a later "big peak" to
help recover the early "first peak", for instance.

Rake receivers (under the name "adaptive equalizers") are also why
digital TV works fairly well in high multipath environments - with
modern receivers that do this.


The real increase in precision comes from the higher sampling rate, i.e. 
sample per chip, which allows for more elaborate schemes to be used. 
Narrow correlation, RAKE etc. is all just different approaches to that, 
but the core comes from the oversampling and increased bandwidth.
Just doing increased bandwidth with traditional correlator is know to 
improve precision as narrow-range multi-path can be better suppressed.
Novatel patented an extension to that using a par of narrow correlators 
to further improve on that aspect.


Regardless how you do it, improved bandwidth and related oversampling 
factor is the enabler, then the weapon of choice to make use of it is 
the next thing to look at.


BTW, I saw that the JPL receiver at ISS got upgraded to support Galileo. 
Cool stuff.


Cheers,
Magnus
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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[jimlux]

On 8/1/17 12:11 PM, Graham / KE9H wrote:

Dider:

This is a CDMA signal. (With a 'chip' rate that far exceeds the information
rate.)

If you put a different correlator on every multipath signal, which are each
differently delayed in time, then they can be independently demodulated.
(Or time shifted and added back together with some quality indicator for
weighting.)
So, in CDMA, multipath is used as a form of (time) diversity reception and
will improve the signal to noise of the combined signal.

By definition, the signal with the least time delay either is, or is
closest to, the most direct path.

You don't have to necessarily fully demodulate this early signal by itself,
just know what its timing is. (And remember where it was, if fading in and
out.)

Since multi-path is a destructive mechanism in most narrow band radio
systems, the above may not be intuitive to people not familiar with CDMA
and "rake receiver" based systems.

Multipath helps, not hurts, these systems, as long as the multipath delays
are most of one chip apart, or more.



For GPS raw (off the air), when they post process at JPL, they use a 
fairly sophisticated correlation process, incorporating an estimator of 
the underlying time delay trajectory: you can use a later "big peak" to 
help recover the early "first peak", for instance.


Rake receivers (under the name "adaptive equalizers") are also why 
digital TV works fairly well in high multipath environments - with 
modern receivers that do this.




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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[jimlux]

On 8/1/17 11:11 AM, Didier Juges wrote:

"The newer the receiver, the more horsepower in the silicon. In the case of
GPS, that
gives you more correlators to do DSP. The sensitivity improvement is a
direct result
of that. If you take a look at the guts of a TBolt, they date to the late
1990’s. That’s
a long time in silicon years …."

It seems that more correlators would speed up the time to first fix, not
necessarily the sensitivity, particularly I do not see how it would
directly affect the capability to stay locked when signal strength
fluctuates?
On the other hand, more correlators may help when there is multipath and a
whole bunch of extraneous signals are fed into the receiver, so maybe the
apparent lack of sensitivity is really the inability to see the signal from
the chaff, not necessarily sensitivity in terms of noise figure.





There's also "more sophisticated correlators" and "more sophisticated 
tracking loops" that are enabled by more computational horsepower.  The 
days of "independent" PN tracking loops for each signal are probably 
long gone, and there's clever "aiding" of the loops by estimating the 
on-the-fly variations.




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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Didier Juges]

" having around 20 dB of gain at the antenna greatly decreases the effect
of feed line loss on noise figure."

And that would be consistent with usage for a timing receiver which is
expected to have a well exposed antenna and a significant line length, as
opposed to navigation receivers where the antenna is expected to have a
short feed line.

On Mon, Jul 31, 2017 at 4:17 PM, Brooke Clarke  wrote:

> Hi Jerry:
>
> The Trimble is the oldest mass produced GPS receiver I know of and because
> the early receivers used high gain antennas it seems that Trimble kept that
> idea for the newer designs. They like about 41 dB gain between the antenna
> and the input to the receiver.
> http://www.prc68.com/I/Trimpack.shtml#Ant
> Newer designs probably place that gain in the front end rather than at the
> antenna.  But having around 20 dB of gain at the antenna gretly decreases
> the effect of feed line loss on noise figure.
>
> --
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
>
>
>  Original Message 
>
>> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
>> antenna placed indoor near a window facing South… can’t get much worse but
>> most of the time it will be locked onto 3 or 4 satellites.I recently
>> bought a www.leobodnar.com   GPSDO for my SDR
>> ham
>> radio setup.  I was very surprised to find that this minimalist GPSDO
>> using
>> a small patch antenna with internal LNA placed near my window had
>> satellite
>> & PPL lock within a few seconds.  It requires 3-4 satellite locks for its
>> PPL.  However, when I attached the patch antenna to my Thunderbolt –
>> satellite signal strength were zero or minus for all satellites.  The
>> specs
>> for the patch antenna are listed below.
>>
>>
>> I would appreciate any advice understanding this behavior.
>>
>>
>> Jerry NY2KW
>>
>>
>> Center Frequency 1575.42MHz±3 MHz
>>
>> V.S.W.R 1.5:1
>>
>> Band Width ±5 MHz
>>
>> Impendence 50 ohm
>>
>> Peak Gain >3dBic Based on 7×7cm ground plane
>>
>> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)
>>
>> Polarization RHCP
>>
>> LNA/Filter
>>
>> LNA Gain (Without cable) 28+/-3dB
>>
>> Noise Figure 1.5dB Typ.
>>
>> Filter Out Band Attenuation (f° =1575.42MHz)
>>
>> 7dB Min f0+/-20MHZ
>>
>> 20dB Min f0+/-50MHZ
>>
>> 30dB Min f0+/-100MHZ
>>
>> V.S.W.R <2.0
>>
>> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other
>>
>> DC Current 5mA /11mA/15mA Max
>>
>>
>>
>>
>> ___
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>> To unsubscribe, go to https://www.febo.com/cgi-bin/m
>> ailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Graham / KE9H]

Dider:

This is a CDMA signal. (With a 'chip' rate that far exceeds the information
rate.)

If you put a different correlator on every multipath signal, which are each
differently delayed in time, then they can be independently demodulated.
(Or time shifted and added back together with some quality indicator for
weighting.)
So, in CDMA, multipath is used as a form of (time) diversity reception and
will improve the signal to noise of the combined signal.

By definition, the signal with the least time delay either is, or is
closest to, the most direct path.

You don't have to necessarily fully demodulate this early signal by itself,
just know what its timing is. (And remember where it was, if fading in and
out.)

Since multi-path is a destructive mechanism in most narrow band radio
systems, the above may not be intuitive to people not familiar with CDMA
and "rake receiver" based systems.

Multipath helps, not hurts, these systems, as long as the multipath delays
are most of one chip apart, or more.

--- Graham

On Tue, Aug 1, 2017 at 1:11 PM, Didier Juges  wrote:

> "The newer the receiver, the more horsepower in the silicon. In the case of
> GPS, that
> gives you more correlators to do DSP. The sensitivity improvement is a
> direct result
> of that. If you take a look at the guts of a TBolt, they date to the late
> 1990’s. That’s
> a long time in silicon years …."
>
> It seems that more correlators would speed up the time to first fix, not
> necessarily the sensitivity, particularly I do not see how it would
> directly affect the capability to stay locked when signal strength
> fluctuates?
> On the other hand, more correlators may help when there is multipath and a
> whole bunch of extraneous signals are fed into the receiver, so maybe the
> apparent lack of sensitivity is really the inability to see the signal from
> the chaff, not necessarily sensitivity in terms of noise figure.
>
>
> On Mon, Jul 31, 2017 at 3:06 PM, Bob kb8tq  wrote:
>
> > Hi
> >
> > > On Jul 31, 2017, at 3:32 PM, Didier Juges  wrote:
> > >
> > > The Thunderbolt is well known for not having the best sensitivity among
> > GPS
> > > receivers. It seems that timing receivers in general, particularly
> those
> > of
> > > the same generation as the Thunderbolt are not as sensitive as
> navigation
> > > (possibly newer) GPS receivers. It may be because they are expected to
> > run
> > > with amplified antennas?
> >
> > The newer the receiver, the more horsepower in the silicon. In the case
> of
> > GPS, that
> > gives you more correlators to do DSP. The sensitivity improvement is a
> > direct result
> > of that. If you take a look at the guts of a TBolt, they date to the late
> > 1990’s. That’s
> > a long time in silicon years ….
> >
> > Bob
> >
> >
> > >
> > > Based on the spec you wrote, it looks like your antenna has no gain, so
> > > definitely I would expect less than good performance.
> > >
> > > My 3 Thunderbolts have been running with inside antennas (2 pucks and
> one
> > > Trimble Bullet) but my ham shack is upstairs and other than the ceiling
> > and
> > > the shingle roof, there are no other obstructions and they are doing OK
> > not
> > > great (all 3 go on holdover somewhat regularly). I am now running one
> > > downstairs (while I work on the new software for the TB Monitor) with
> 50
> > > feet of RG-58 going to a HP 58532A antenna somewhat in the clear but
> > only 8
> > > feet above ground with significant obstructions in pretty much all
> > > directions due to the low height and the Thunderbolt is happy as a clam
> > in
> > > spite of the significant losses in the cable. The HP antenna works much
> > > better than the Trimble Bullet antenna.
> > >
> > > On Mon, Jul 31, 2017 at 12:19 PM, Jerry  wrote:
> > >
> > >> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
> > >> antenna placed indoor near a window facing South… can’t get much worse
> > but
> > >> most of the time it will be locked onto 3 or 4 satellites.I
> recently
> > >> bought a www.leobodnar.com   GPSDO for my
> SDR
> > >> ham
> > >> radio setup.  I was very surprised to find that this minimalist GPSDO
> > using
> > >> a small patch antenna with internal LNA placed near my window had
> > satellite
> > >> & PPL lock within a few seconds.  It requires 3-4 satellite locks for
> > its
> > >> PPL.  However, when I attached the patch antenna to my Thunderbolt –
> > >> satellite signal strength were zero or minus for all satellites.  The
> > specs
> > >> for the patch antenna are listed below.
> > >>
> > >>
> > >>
> > >> I would appreciate any advice understanding this behavior.
> > >>
> > >>
> > >>
> > >> Jerry NY2KW
> > >>
> > >>
> > >>
> > >> Center Frequency 1575.42MHz±3 MHz
> > >>
> > >> V.S.W.R 1.5:1
> > >>
> > >> Band Width ±5 MHz
> > >>
> > >> Impendence 50 ohm
> > >>
> > >> Peak Gain >3dBic Based on 7×7cm ground plane
> > >>
> > >> Gain 

Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Didier Juges]

"The newer the receiver, the more horsepower in the silicon. In the case of
GPS, that
gives you more correlators to do DSP. The sensitivity improvement is a
direct result
of that. If you take a look at the guts of a TBolt, they date to the late
1990’s. That’s
a long time in silicon years …."

It seems that more correlators would speed up the time to first fix, not
necessarily the sensitivity, particularly I do not see how it would
directly affect the capability to stay locked when signal strength
fluctuates?
On the other hand, more correlators may help when there is multipath and a
whole bunch of extraneous signals are fed into the receiver, so maybe the
apparent lack of sensitivity is really the inability to see the signal from
the chaff, not necessarily sensitivity in terms of noise figure.


On Mon, Jul 31, 2017 at 3:06 PM, Bob kb8tq  wrote:

> Hi
>
> > On Jul 31, 2017, at 3:32 PM, Didier Juges  wrote:
> >
> > The Thunderbolt is well known for not having the best sensitivity among
> GPS
> > receivers. It seems that timing receivers in general, particularly those
> of
> > the same generation as the Thunderbolt are not as sensitive as navigation
> > (possibly newer) GPS receivers. It may be because they are expected to
> run
> > with amplified antennas?
>
> The newer the receiver, the more horsepower in the silicon. In the case of
> GPS, that
> gives you more correlators to do DSP. The sensitivity improvement is a
> direct result
> of that. If you take a look at the guts of a TBolt, they date to the late
> 1990’s. That’s
> a long time in silicon years ….
>
> Bob
>
>
> >
> > Based on the spec you wrote, it looks like your antenna has no gain, so
> > definitely I would expect less than good performance.
> >
> > My 3 Thunderbolts have been running with inside antennas (2 pucks and one
> > Trimble Bullet) but my ham shack is upstairs and other than the ceiling
> and
> > the shingle roof, there are no other obstructions and they are doing OK
> not
> > great (all 3 go on holdover somewhat regularly). I am now running one
> > downstairs (while I work on the new software for the TB Monitor) with 50
> > feet of RG-58 going to a HP 58532A antenna somewhat in the clear but
> only 8
> > feet above ground with significant obstructions in pretty much all
> > directions due to the low height and the Thunderbolt is happy as a clam
> in
> > spite of the significant losses in the cable. The HP antenna works much
> > better than the Trimble Bullet antenna.
> >
> > On Mon, Jul 31, 2017 at 12:19 PM, Jerry  wrote:
> >
> >> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
> >> antenna placed indoor near a window facing South… can’t get much worse
> but
> >> most of the time it will be locked onto 3 or 4 satellites.I recently
> >> bought a www.leobodnar.com   GPSDO for my SDR
> >> ham
> >> radio setup.  I was very surprised to find that this minimalist GPSDO
> using
> >> a small patch antenna with internal LNA placed near my window had
> satellite
> >> & PPL lock within a few seconds.  It requires 3-4 satellite locks for
> its
> >> PPL.  However, when I attached the patch antenna to my Thunderbolt –
> >> satellite signal strength were zero or minus for all satellites.  The
> specs
> >> for the patch antenna are listed below.
> >>
> >>
> >>
> >> I would appreciate any advice understanding this behavior.
> >>
> >>
> >>
> >> Jerry NY2KW
> >>
> >>
> >>
> >> Center Frequency 1575.42MHz±3 MHz
> >>
> >> V.S.W.R 1.5:1
> >>
> >> Band Width ±5 MHz
> >>
> >> Impendence 50 ohm
> >>
> >> Peak Gain >3dBic Based on 7×7cm ground plane
> >>
> >> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)
> >>
> >> Polarization RHCP
> >>
> >> LNA/Filter
> >>
> >> LNA Gain (Without cable) 28+/-3dB
> >>
> >> Noise Figure 1.5dB Typ.
> >>
> >> Filter Out Band Attenuation (f° =1575.42MHz)
> >>
> >> 7dB Min f0+/-20MHZ
> >>
> >> 20dB Min f0+/-50MHZ
> >>
> >> 30dB Min f0+/-100MHZ
> >>
> >> V.S.W.R <2.0
> >>
> >> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other
> >>
> >> DC Current 5mA /11mA/15mA Max
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> ___
> >> time-nuts mailing list -- time-nuts@febo.com
> >> To unsubscribe, go to https://www.febo.com/cgi-bin/
> >> mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >>
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> > and follow the instructions there.
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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Brooke Clarke]

Hi Jerry:

The Trimble is the oldest mass produced GPS receiver I know of and because the early receivers used high gain antennas 
it seems that Trimble kept that idea for the newer designs. They like about 41 dB gain between the antenna and the input 
to the receiver.

http://www.prc68.com/I/Trimpack.shtml#Ant
Newer designs probably place that gain in the front end rather than at the antenna.  But having around 20 dB of gain at 
the antenna gretly decreases the effect of feed line loss on noise figure.


--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

 Original Message 

Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
antenna placed indoor near a window facing South… can’t get much worse but
most of the time it will be locked onto 3 or 4 satellites.I recently
bought a www.leobodnar.com   GPSDO for my SDR ham
radio setup.  I was very surprised to find that this minimalist GPSDO using
a small patch antenna with internal LNA placed near my window had satellite
& PPL lock within a few seconds.  It requires 3-4 satellite locks for its
PPL.  However, when I attached the patch antenna to my Thunderbolt –
satellite signal strength were zero or minus for all satellites.  The specs
for the patch antenna are listed below.

  


I would appreciate any advice understanding this behavior.

  


Jerry NY2KW

  


Center Frequency 1575.42MHz±3 MHz

V.S.W.R 1.5:1

Band Width ±5 MHz

Impendence 50 ohm

Peak Gain >3dBic Based on 7×7cm ground plane

Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)

Polarization RHCP

LNA/Filter

LNA Gain (Without cable) 28+/-3dB

Noise Figure 1.5dB Typ.

Filter Out Band Attenuation (f° =1575.42MHz)

7dB Min f0+/-20MHZ

20dB Min f0+/-50MHZ

30dB Min f0+/-100MHZ

V.S.W.R <2.0

DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other

DC Current 5mA /11mA/15mA Max

  

  

  


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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Bob kb8tq]

Hi

> On Jul 31, 2017, at 3:32 PM, Didier Juges  wrote:
> 
> The Thunderbolt is well known for not having the best sensitivity among GPS
> receivers. It seems that timing receivers in general, particularly those of
> the same generation as the Thunderbolt are not as sensitive as navigation
> (possibly newer) GPS receivers. It may be because they are expected to run
> with amplified antennas?

The newer the receiver, the more horsepower in the silicon. In the case of GPS, 
that
gives you more correlators to do DSP. The sensitivity improvement is a direct 
result
of that. If you take a look at the guts of a TBolt, they date to the late 
1990’s. That’s 
a long time in silicon years ….

Bob


> 
> Based on the spec you wrote, it looks like your antenna has no gain, so
> definitely I would expect less than good performance.
> 
> My 3 Thunderbolts have been running with inside antennas (2 pucks and one
> Trimble Bullet) but my ham shack is upstairs and other than the ceiling and
> the shingle roof, there are no other obstructions and they are doing OK not
> great (all 3 go on holdover somewhat regularly). I am now running one
> downstairs (while I work on the new software for the TB Monitor) with 50
> feet of RG-58 going to a HP 58532A antenna somewhat in the clear but only 8
> feet above ground with significant obstructions in pretty much all
> directions due to the low height and the Thunderbolt is happy as a clam in
> spite of the significant losses in the cable. The HP antenna works much
> better than the Trimble Bullet antenna.
> 
> On Mon, Jul 31, 2017 at 12:19 PM, Jerry  wrote:
> 
>> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
>> antenna placed indoor near a window facing South… can’t get much worse but
>> most of the time it will be locked onto 3 or 4 satellites.I recently
>> bought a www.leobodnar.com   GPSDO for my SDR
>> ham
>> radio setup.  I was very surprised to find that this minimalist GPSDO using
>> a small patch antenna with internal LNA placed near my window had satellite
>> & PPL lock within a few seconds.  It requires 3-4 satellite locks for its
>> PPL.  However, when I attached the patch antenna to my Thunderbolt –
>> satellite signal strength were zero or minus for all satellites.  The specs
>> for the patch antenna are listed below.
>> 
>> 
>> 
>> I would appreciate any advice understanding this behavior.
>> 
>> 
>> 
>> Jerry NY2KW
>> 
>> 
>> 
>> Center Frequency 1575.42MHz±3 MHz
>> 
>> V.S.W.R 1.5:1
>> 
>> Band Width ±5 MHz
>> 
>> Impendence 50 ohm
>> 
>> Peak Gain >3dBic Based on 7×7cm ground plane
>> 
>> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)
>> 
>> Polarization RHCP
>> 
>> LNA/Filter
>> 
>> LNA Gain (Without cable) 28+/-3dB
>> 
>> Noise Figure 1.5dB Typ.
>> 
>> Filter Out Band Attenuation (f° =1575.42MHz)
>> 
>> 7dB Min f0+/-20MHZ
>> 
>> 20dB Min f0+/-50MHZ
>> 
>> 30dB Min f0+/-100MHZ
>> 
>> V.S.W.R <2.0
>> 
>> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other
>> 
>> DC Current 5mA /11mA/15mA Max
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Didier Juges]

The Thunderbolt is well known for not having the best sensitivity among GPS
receivers. It seems that timing receivers in general, particularly those of
the same generation as the Thunderbolt are not as sensitive as navigation
(possibly newer) GPS receivers. It may be because they are expected to run
with amplified antennas?

Based on the spec you wrote, it looks like your antenna has no gain, so
definitely I would expect less than good performance.

My 3 Thunderbolts have been running with inside antennas (2 pucks and one
Trimble Bullet) but my ham shack is upstairs and other than the ceiling and
the shingle roof, there are no other obstructions and they are doing OK not
great (all 3 go on holdover somewhat regularly). I am now running one
downstairs (while I work on the new software for the TB Monitor) with 50
feet of RG-58 going to a HP 58532A antenna somewhat in the clear but only 8
feet above ground with significant obstructions in pretty much all
directions due to the low height and the Thunderbolt is happy as a clam in
spite of the significant losses in the cable. The HP antenna works much
better than the Trimble Bullet antenna.

On Mon, Jul 31, 2017 at 12:19 PM, Jerry  wrote:

> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
> antenna placed indoor near a window facing South… can’t get much worse but
> most of the time it will be locked onto 3 or 4 satellites.I recently
> bought a www.leobodnar.com   GPSDO for my SDR
> ham
> radio setup.  I was very surprised to find that this minimalist GPSDO using
> a small patch antenna with internal LNA placed near my window had satellite
> & PPL lock within a few seconds.  It requires 3-4 satellite locks for its
> PPL.  However, when I attached the patch antenna to my Thunderbolt –
> satellite signal strength were zero or minus for all satellites.  The specs
> for the patch antenna are listed below.
>
>
>
> I would appreciate any advice understanding this behavior.
>
>
>
> Jerry NY2KW
>
>
>
> Center Frequency 1575.42MHz±3 MHz
>
> V.S.W.R 1.5:1
>
> Band Width ±5 MHz
>
> Impendence 50 ohm
>
> Peak Gain >3dBic Based on 7×7cm ground plane
>
> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)
>
> Polarization RHCP
>
> LNA/Filter
>
> LNA Gain (Without cable) 28+/-3dB
>
> Noise Figure 1.5dB Typ.
>
> Filter Out Band Attenuation (f° =1575.42MHz)
>
> 7dB Min f0+/-20MHZ
>
> 20dB Min f0+/-50MHZ
>
> 30dB Min f0+/-100MHZ
>
> V.S.W.R <2.0
>
> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other
>
> DC Current 5mA /11mA/15mA Max
>
>
>
>
>
>
>
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Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas

[Arnold Tibus]

Hello Jerry,
I think the problem is not at the antenna, I consider the 58532A to be a
lot better than these smal patch antennas.
But the point is that modern receivers have a significant better sensivity!
In my opinion, indoor position of any kind of antenna is not a good
solution if you want to get
low jitter results. Indoor antennas do get mostly indirect reception via
reflections oft the
SAT-signals, so even the position indicated is not really precise.
When possible, any antenna should be positioned to get a free view to
the sky 360 deg
and at least about 20 deg in elevation.
My antenna is mounted on the top of the roof outside at the highest
point with abt.
10m coax cable down to my good old thunderbolt providing best reception
possible.

I wish you good luck for your further investigations,

73
Arnold, DK2WT

Am 31.07.2017 um 19:19 schrieb Jerry:
> Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
> antenna placed indoor near a window facing South… can’t get much worse but
> most of the time it will be locked onto 3 or 4 satellites.I recently
> bought a www.leobodnar.com   GPSDO for my SDR ham
> radio setup.  I was very surprised to find that this minimalist GPSDO using
> a small patch antenna with internal LNA placed near my window had satellite
> & PPL lock within a few seconds.  It requires 3-4 satellite locks for its
> PPL.  However, when I attached the patch antenna to my Thunderbolt –
> satellite signal strength were zero or minus for all satellites.  The specs
> for the patch antenna are listed below.
>
>  
>
> I would appreciate any advice understanding this behavior.
>
>  
>
> Jerry NY2KW
>
>  
>
> Center Frequency 1575.42MHz±3 MHz
>
> V.S.W.R 1.5:1
>
> Band Width ±5 MHz
>
> Impendence 50 ohm
>
> Peak Gain >3dBic Based on 7×7cm ground plane
>
> Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)
>
> Polarization RHCP
>
> LNA/Filter
>
> LNA Gain (Without cable) 28+/-3dB
>
> Noise Figure 1.5dB Typ.
>
> Filter Out Band Attenuation (f° =1575.42MHz)
>
> 7dB Min f0+/-20MHZ
>
> 20dB Min f0+/-50MHZ
>
> 30dB Min f0+/-100MHZ
>
> V.S.W.R <2.0
>
> DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other
>
> DC Current 5mA /11mA/15mA Max
>
>  
>
>  
>
>  
>
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[time-nuts] Thunderbolt - trouble locking with some types of antennas

[Jerry]

Due to access problems, I run my Thunderbolt with a Symmetricom 58532A
antenna placed indoor near a window facing South… can’t get much worse but
most of the time it will be locked onto 3 or 4 satellites.I recently
bought a www.leobodnar.com   GPSDO for my SDR ham
radio setup.  I was very surprised to find that this minimalist GPSDO using
a small patch antenna with internal LNA placed near my window had satellite
& PPL lock within a few seconds.  It requires 3-4 satellite locks for its
PPL.  However, when I attached the patch antenna to my Thunderbolt –
satellite signal strength were zero or minus for all satellites.  The specs
for the patch antenna are listed below.

 

I would appreciate any advice understanding this behavior.

 

Jerry NY2KW

 

Center Frequency 1575.42MHz±3 MHz

V.S.W.R 1.5:1

Band Width ±5 MHz

Impendence 50 ohm

Peak Gain >3dBic Based on 7×7cm ground plane

Gain Coverage >-4dBic at –90°<0<+90°(over 75% Volume)

Polarization RHCP

LNA/Filter

LNA Gain (Without cable) 28+/-3dB

Noise Figure 1.5dB Typ.

Filter Out Band Attenuation (f° =1575.42MHz)

7dB Min f0+/-20MHZ

20dB Min f0+/-50MHZ

30dB Min f0+/-100MHZ

V.S.W.R <2.0

DC Voltage 2.7V/3.0V/3.3V/5.0V/3.0V to 5.0V/other

DC Current 5mA /11mA/15mA Max

 

 

 

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